1. Field of the Invention
The invention relates to a micromechanical electrostatic relay having
a base substrate with a base electrode and with at least one stationary contact, PA1 a metal carrier layer is applied, with the interposition of an insulating layer and an intermediate space, to a base substrate which is provided with a metal layer as the base electrode, PA1 two spring tongues which are linked on one side and whose free ends are opposite one another are formed in the carrier layer, PA1 at least in places, the spring tongues are provided with a tensile stress layer on their top surface, PA1 a--preferably shorter--spring tongue is provided at its free end with at least one stationary contact, PA1 the--preferably longer--spring tongue is provided with at least one moving contact which overlaps the stationary contact, with the interposition of a sacrificial layer, and PA1 the curvature of the spring tongues upwards away from the substrate is achieved by etching the spring tongues free from one another and from the substrate.
an armature spring tongue which is linked on one side to a carrier layer connected to the base substrate, has an armature electrode opposite the base electrode, is elastically curved away from the base substrate in the rest state forming a wedge-shaped air gap, and is fitted at its free end with at least one moving contact opposite the stationary contact. In addition, the invention relates to a method for producing such a relay.
2. Description of the Prior Art
Such a micromechanical relay and an appropriate production method have already been disclosed, in principle, in German Patent Document No. 42 05 029 C1. The essential feature in this case is that the armature spring tongue, which is exposed from a substrate, is curved in such a manner that the armature electrode forms a wedge-shaped air gap with the opposite base electrode, which air gap, when a voltage is applied between the two electrodes, produces a rapid attraction movement on the basis of the so-called moving-wedge principle. Refinements of this principle have been disclosed, for example, in German Patent Document No. 44 37 259 C1 and German Patent Document No. 44 37 261 C1.
In the case of all these known relays with a micromechanical construction, a relatively high manufacturing effort is involved since two substrates, namely on the one hand a base substrate with the base electrode and the stationary contact, and on the other hand an armature substrate with the armature spring tongue, the armature electrode and the moving contact, have to be produced separately and connected to one another. In addition to the said main functional elements of the two substrates, further coating and etching processes are involved, for example for insulating layers, leads and the like. Each of the two substrates therefore has to be subjected on its own to all of the complex processes involved before their main functional layers can be connected, facing one another. Since the switching elements are also intended to be protected against environmental influences, an additional covering part is, as a rule, required as a closing element, although there is no need to describe this in any more detail.
In order to simplify production, it would be desirable if it were possible to form all the functional elements of the relay on a substrate from one side. In this case, it is in principle feasible to form a stationary contact element and a spring tongue with a moving contact on one and the same substrate, in which case, for example, the stationary contact and the moving contact can be produced one above the other, and the contact gap can be formed by etching away a so-called sacrificial layer. Such an arrangement has been disclosed in principle in U.S. Pat. No. 4,570,139. However, in the case of the micromechanical switch there, a cavity that is not accurately defined is created underneath the armature spring tongue, and this cavity is not suitable for the formation of an electrostatic drive. In the case of the switch there, provision is therefore made for both the armature spring tongue as well as the stationary contact to be provided with a magnetic layer in each case, and for the switch to be operated via an externally applied magnetic field. Even in the case of the relatively short contact gap which can be achieved between the moving contact and the rigid stationary contact using the sacrificial layer technique, such a magnetic field can be used to produce the required contact force. However, to do this, an additional device is required to produce the magnetic field, for example a coil, and this occupies considerably more space than is available for a micromechanical relay in certain aplications.